Cx43 in a Genetic Model of Altered Myocardial Conduction

这项研究的目的是确定Cx43在正常心脏传导中的功能作用，并描述缝隙连接偶联改变在传导障碍和心律失常发病机制中的作用。拟议的实验将使用编码主要心脏缝隙连接蛋白Cx43的基因的零等位基因杂合子的小鼠(Cx43加/减小鼠)进行。这些小鼠产生50%的野生型Cx43，并显著减少了连接心室肌细胞的缝隙连接的数量。成年小鼠Cx43表达减少的功能后果是心室传导速度减慢25%-30%。然而，在生理条件下，Cx43加/减小鼠的电生理表型是微妙的，而在病理生理条件下，可以诱导出更戏剧性的表型。在对急性局部缺血的反应中，Cx43+/-小鼠表现出发病加快，室性心律失常的发生率、频率和持续时间增加。这项拟议的研究集中于确定偶联减少促进急性和慢性缺血性心脏病心律失常的机制。具体目标1的研究将阐明缝隙连接处电解偶联的速度和程度与急性缺血诱发的室性快速性心律失常的发生之间的机制关系。具体目标2的研究将确定急性冠状动脉闭塞后Cx43+/-的心律失常机制，并描述Cx43和改变的细胞间耦合在电触发事件和持续传导异常中的作用，这些事件是急性心肌缺血引发和维持室性心律失常的基础。在具体目标3中，将通过比较Cx43+/-和野生型小鼠心肌梗死愈合后的心律失常发生情况，阐明缝隙连接重构在慢性缺血性心脏病心律失常发病机制中的作用。在特定目标4中，将使用生长在特定结构和填充几何形状的图案化阵列中的新生小鼠心室肌细胞来描绘传导的分子和结构决定因素，并通过高分辨率光学映射进行分析。拟议的研究结果将确定减少偶联促进患者急性和慢性缺血性心脏病小鼠模型室性快速性心律失常的机制。

The goal of the proposed research is to define the functional role of Cx43 in normal cardiac conduction and to delineate the role of altered coupling at gap junctions in the pathogenesis of conduction disturbances and arrhythmias. Proposed experiments will be performed using mice that are heterozygous for a null allele for the gene encoding the major cardiac gap junction protein, Cx43 (Cx43 plus/minus mice). These mice produce 50 percent of the wildtype level of Cx43 and have significant reduction in the number of gap junction interconnecting ventricular myocytes. The functional consequence of reduced Cx43 expression in adult mice is a 25-30 percent slowing of ventricular conduction velocity. Whereas the electrophysiological phenotype in Cx43 plus/minus mice is subtle under physiological conditions, a more dramatic phenotype can be elicited under pathophysiological condition. In response to acute regional ischemia, Cx43 plus/minus mice exhibit accelerated onset and increased incidence, frequency and duration of ventricular arrhythmias. The proposed research is focused on defining mechanisms by which reduced coupling promotes arrhythmias in accute and chronic ischemic heart disease. Studies in Specific Aim 1 will elucidate the mechanistic relationship between the rate and extent of electrical uncoupling at gap junctions and development of ventricular tachyarrhythmias induced by acute ischemia. Studies in Specific Aim 2 will define arrhythmia mechanisms in Cx43 plus/minus following acute coronary occlusion and delineate the roles of Cx43 and altered cell-to- cell coupling in electrical triggering events and sustained conduction abnormalities that underlie initiation and maintenance of ventricular arrhythmias in the setting of acute myocardial ischemia. In Specific Aim 3, the role of gap junction remodeling in the pathogenesis of arrhythmias in chronic ischemic heart disease will be elucidated by comparing arrhythmogenesis in Cx43 plus/minus and wildtype mice with healed myocardial infarcts. And in Specific Aim 4, molecular and structural determinants of conduction will be delineated using neonatal mouse ventricular myocytes grown in patterned arrays of defined structure and packing geometry, and analyzed by high resolution optical mapping. The results of the proposed research will define mechanisms by which reduced coupling promotes ventricular tachyarrhythmias in mouse models of acute and chronic ischemic heart disease in patients.